Re: [PATCH v2 1/4] eal: add bitset type

[David Marchand <david.marchand@redhat.com>]

On Thu, Oct 10, 2024 at 10:30 AM David Marchand
<david.marchand@redhat.com> wrote:
> diff --git a/lib/eal/include/rte_bitset.h b/lib/eal/include/rte_bitset.h
> new file mode 100644
> index 0000000000..b2d71aa7c6
> --- /dev/null
> +++ b/lib/eal/include/rte_bitset.h

[snip]

> +__rte_experimental
> +static inline ssize_t
> +__rte_bitset_find_nowrap(const uint64_t *bitset, size_t __rte_unused size, size_t start_bit,
> +               size_t len, bool find_clear)
> +{
> +       size_t word_idx;
> +       size_t offset;
> +       size_t end_bit = start_bit + len;
> +
> +       RTE_ASSERT(end_bit <= size);
> +
> +       if (unlikely(len == 0))
> +               return -1;
> +
> +       word_idx = __RTE_BITSET_WORD_IDX(start_bit);
> +       offset = __RTE_BITSET_BIT_OFFSET(start_bit);
> +
> +       while (word_idx <= __RTE_BITSET_WORD_IDX(end_bit - 1)) {
> +               uint64_t word;
> +               int word_ffs;
> +
> +               word = bitset[word_idx];
> +               if (find_clear)
> +                       word = ~word;
> +
> +               word >>= offset;
> +
> +               word_ffs = __builtin_ffsll(word);
> +
> +               if (word_ffs != 0) {
> +                       ssize_t ffs = start_bit + word_ffs - 1;
> +
> +                       /*
> +                        * Check if set bit were among the last,
> +                        * unused bits, in the last word.
> +                        */
> +                       if (unlikely(ffs >= (ssize_t)end_bit))
> +                               return -1;
> +
> +                       return ffs;
> +               }
> +
> +               start_bit += (RTE_BITSET_WORD_BITS - offset);
> +               word_idx++;
> +               offset = 0;
> +       }
> +
> +       return -1;
> +
> +}

Now that the series is merged, we finally got one report from UNH and
this patch breaks MSVC build.

FAILED: lib/librte_eal.a.p/eal_common_rte_bitset.c.obj
"cl" "-Ilib\librte_eal.a.p" "-Ilib" "-I..\lib" "-I." "-I.." "-Iconfig"
"-I..\config" "-Ilib\eal\include" "-I..\lib\eal\include"
"-Ilib\eal\windows\include" "-I..\lib\eal\windows\include"
"-Ilib\eal\x86\include" "-I..\lib\eal\x86\include" "-Ilib\eal\common"
"-I..\lib\eal\common" "-Ilib\eal" "-I..\lib\eal" "-Ilib\log"
"-I..\lib\log" "-Ilib\kvargs" "-I..\lib\kvargs" "-IC:\Program
Files\Mellanox\MLNX_WinOF2_DevX_SDK\inc" "/MD" "/nologo"
"/showIncludes" "/W3" "/WX" "/std:c11" "/O2" "/Gw" "/wd4244" "/wd4267"
"/wd4146" "/experimental:c11atomics" "/d1experimental:typeof"
"/experimental:statementExpressions" "/FI" "rte_config.h"
"-D_GNU_SOURCE" "-D_WIN32_WINNT=0x0A00" "-DALLOW_EXPERIMENTAL_API"
"-DALLOW_INTERNAL_API" "-DABI_VERSION=\"25.0\""
"-DRTE_LOG_DEFAULT_LOGTYPE=lib.eal"
"/Fdlib\librte_eal.a.p\eal_common_rte_bitset.c.pdb"
/Folib/librte_eal.a.p/eal_common_rte_bitset.c.obj "/c"
../lib/eal/common/rte_bitset.c
..\lib\eal\include\rte_bitset.h(612): error C2220: the following
warning is treated as an error
..\lib\eal\include\rte_bitset.h(612): warning C4013: '__builtin_ffsll'
undefined; assuming extern returning int


I see two options:
- rewrite this code and use existing rte_ctz64 or rte_bsf64_safe,
- introduce an additional rte_ffs64() in rte_bitops.h and implement it
for MSVC and others,

And I would prefer we extend checkpatch, so that such issue is caught earlier.
See:
devtools/checkpatches.sh:               -v
EXPRESSIONS='\\<__builtin_(clz|clzll|ctz|ctzll|popcount|popcountll)\\>'
\

Please send a fix.


-- 
David Marchand